This invention relates to apparatus and methods for installing and energizing submergible pumps in underwater wells.
Increasing demand and price of petroleum products have stimulated great interest in subsea exploration for and production of oil and gas. Until recently these activities have centered around offshore platforms, but with the need for operating at greater depths and with greater flexibility, subsea wells remote from or even independent of offshore platforms have become more attractive. Such subsea wells may have production trees that are remotely or automatically controlled, with production tubing extending along the ocean floor to a remote depot.
Installing and energizing submergible pumps in such subsea wells involve difficult problems. Running and pulling operations are expensive and should be minimized and simplified to the extent possible.
When submergible pumps are employed in onshore wells, the pump motor may be energized from a cable that extends through a packing at the wellhead. In subsea wells such energization of the pump is not practical because of the difficulty of providing adequate seals around the cable extending from the wellhead. The avoidance of oil spills has very high priority.
Accordingly, attempts have been made to suspend the submergible pump in the well from a suspension head that seats in the wellhead apparatus and that has an electrical connector part engaging a mating electrical connector part on the wellhead apparatus to supply electrical energy to the pump. In theory, this concept is highly advantageous, since it is unnecessary to run a power cable through seals or packings that must be opened to install or remove the pump. In practice, however, the technique leaves much to be desired. Providing good, long-lasting electrical contacts capable of carrying heavy currents in an environment contaminated by well fluid is a problem not easily solved.
Accordingly, an object of the present invention is to provide an improved apparatus and method for installing and energizing submergible pumps in underwater wells.
Another object of the invention is to provide improved electrical connectors.
A further object of the invention is to provide improved apparatus and methods for making good, long-lasting, electrical contacts at a contact region that is contaminated.
Still another object of the invention is to provide improved apparatus and methods for cleansing, insulating, and sealing an electrical contact region, particularly in an underwater wellhead.
Briefly stated, in one of the broad aspects of the invention, apparatus for underwater electrical connections and the like, comprises a first member having a space therein with first electrical contact means at a contact region of the space, a second member adapted to be received in said space and having second electrical contact means adapted to engage the first contact means, means for supplying fluid to the contact region to cleanse the region, and means for exhausting the fluid from the region.
In another of the broad aspects of the invention, underwater electrical connector apparatus and the like comprises a first member having a bore therein with a first set of contacts at a contact region, a second member adapted to enter the bore and having a second set of contacts adapted to engage corresponding contacts of the first set, and means for locking the members together with the contacts engaged, at least some of the contacts being annular and being disposed about the axis of the bore.
In a further broad aspect of the invention, a method of installing and energizing an electric submergible pump in an underwater well comprises providing at an underwater wellhead a spool having a bore aligned with the well and having a first set of electrical contacts at a contact region of the bore, suspending the pump from a suspension head having a second set of contacts adapted to engage corresponding contacts of the first, lowering the suspension head and the pump into the bore with the pump passing through the bore into the well, and with the contacts of the second set positioned for engagement with the corresponding contacts of the first set, passing a cleaning fluid through the contact region of the bore, fixing the suspension head in the bore, and sealing the contact region of the bore so as to exclude well fluid therefrom.